Continuous-current generator.



K. GREUNER.

CONTINUOUS CURRENT GENERATOR APPLICATION FILED 11.11115, 1911.

Patented Mar. 10, 19%

UNITED STATES PATENT KURT GREUNER, OF ESSEN-ON-THE-RUHR, GERMANY, ASSIGNOR- TO FRIED. KRUPP AKTIENGESELLSCHAFT, OF ESSEN-ON-TI-IE-RUI-IR, GER-MANY.

CONTINUOUS-CURRENT GENERATOR.

Specification of Letters Patent.

Application filed May 15, 1911.

To all whom it may concern Be it known that I, KURT GREUNER, a subject of the Emperor of Germany, and a resident of Essen-on-the-Ruhr, Germany, have invented certain new and useful Improvements in Continuous-Current Generators, of which the following is a specification.

In operating electro-motors which are arranged in so called Leonard-connection and are fed by a separately excited generator with compounding winding, it is desirable that the motor, even in its unloaded state, with certainty stands still when the separate excitation is cut off; and also that the remanent current which appears when the motor stands still may become as small as possible.

Figures 1 and 2 give diagrammatical representations of the currents; Fig. 3 gives an embodiment of the invention represent-- ing a longitudinal section of the generator; and Fig. A front and rear-end views of Fig. 3.

The conditions obtained with disconnected separate excitation are diagrammatically shown in Fig. 1 on the drawing. The abscissas measured in the direction of the axis M A express the strength of the armature current of the generator,and the ordinates measured in the direction of the axis M B, the magnitude of the corresponding tension. If the generator has no other field winding beside the separately excited winding and the compounding winding, it will deliver an electromotive force which is a combination of the remanent tension and the tension generated by the compounding winding. The remanent tension is in Fig. 1 expressed by a line 0, parallel to the abscissaaxis H A and intersecting the ordinate axis M B at the point C. The curve d, Fig. 2, represents the characteristic of the compounding winding relative to the strength of the armature current, and has been drawn in the usual manner as regards the coordinate system A M B, which corresponds to the coordinate system A M B in Fig. 1. Drawing now this curve (Z in the same relation to lines 0 and C B in Fig. 1, as it has to the coordinate axes M A and M B in Fig. 2, a curve cl will be pro duced, the ordinates of which will represent the sum of the remanent tension and the tension generated by the compounding winding. In other words, it 'epresents the course of the electromotive force of the generator with the separate excitation cut out. The curve (Z intersects at a point F a straight line 6 running through the origin M of coordinates, which line represents the voltage drop, caused by the resistance of the circuit; and which line will briefly be called resistance line; the abscissa M G of this point F representing the greatest current strength which would be obtainable with disconnected separate excitation. Should the strength of the armature current represented by the abscissa M G be smaller than that of the current expressing the starting moment of the motor, the motor will be at rest when the separate excitation is disconnected, and a remanent current will be produced, the magnitude of which is repre sented by the length of M G.

In order to get the remanent current as small as possible, which is very desirable, it must be so arranged that the intersection between the resistance line and the curve (representing the course of the electromotive force of the generator with the separate excitation cut out) is situated as near as possible to the starting point M of the coordinates. To accomplish this, a differential compound winding to weaken the field has before now been used.

The present invention relates to an arrangement of this kind of generators, wherein the desired object can be reached in a more complet way.

The present invention consists in arranging the differential compound winding on a separate magnet frame, the saturation point of which has been chosen so low that the field strength of this magnet frame is influenced by the exciting current of the opposing winding only up to a comparatively low current strength.

Figs. 3 and A give a diagrammatical representation of one embodiment of the invention, of which Fig. 3 represents a longitudinal section of the generator and Fig. A front and rear end views. H represents the principal magnet frame with the separately excited field-winding N and the compounding winding D, andJ represents the special magnet frame carrying the differential compound winding K for weakening the field. As indicated in Fig. 4, the windings D and K are arranged in series. The saturation point of the magnet frame J lies so low, that the field strength of this magnet frame is substantially influenced only up to a comparatively low current strength by the exciting current of the differential compound winding K. In consequence hereof the characteristic of the differential compound winding K, referred to the strength of the armature current, runs almost parallel to the abscissa-axis M A, starting from'a comparatively low value of the current strength. This is shown in Fig. 2, the course being indicated by the curve 70, drawn in the same direction as the characteristic (Z of the compound winding D. The sections of the ordinates lying between these curves (Z and 7: represent the ordinates otthe resultant characteristic of the windings D and K. The resultant characteristic of the windings D and K will then be represented by a curve 72 obtained by laying off against the abscissa-axis M A the lengths of the ordinates cut off between curves (Z and 7c. The proportion is so chosen that the charac teristic 7c in the beginning runs steeper than the characteristic (Z so that the corresponding part of the resultant characteristic n will have negative ordinates. If now the curve a is laid off against lines 0 and C B in Fig. 1, in a similar position to what it has in Fig. 2 relative to the coordinate axes M A and M B, a curve a" will be obtained, that represents the resultant electromotive force produced in a generator provided with compound and differential compound windings and having the separate excitation disconnected. lVith the highest possible remanent tension, represented by the line 0, it would still be possible, as Fig. 1 shows, to attain that the curve a intersects the resistance line 6 in a point F, lying very close to the beginning M of the coordinates; and that beyond the point F, it continues to run below the resistance line 6. It is particularly advantageous in this relation, when the proportions, as indicated above, are so chosen, that the characteristic is of the differential compound winding, to commence with, runs steeper than the characteristic (Z of the compounding winding so that the resulting characteristic it runs at first below the abscissa-axis M A. As the intersecting point F is situated very close to the start ing point M of the coordinates, the remanent current represented by the abscissa M G of the point F will be exceedingly small, and the smaller the remanent tension is, the smaller said current will be, which may be easily seen from Fig. 1. It is also desirable to choose the proportion in such a manner that the curve a on the other side of point F runs as near as possible parallel to theresistance line 6. In that case, a curve 3), Fig. 1, will be obtained of the resultant electromotive force of the generator when the separate excitation is connected, which curve 7) will run as nearly parallel to the reslstance line 6 as the curve a, 1ts

ordinates being proportionately larger than the corresponding ordinates of the curve a. This circumstance is particularly advantageous if the motor has to run with very low speed (with few revolutions per minute). I11 the case illustrated in Fig. 1, the curve p within the range in question, is situated only very slightly above the resistance line 6, proportionate to the number or revolutions of the motor. If the curve 7) does not run approximately parallel to the resistance line 6, even a slight change in load would have a considerable influence on the number of revolutions or" the motor (the Il'lOtOlI speed) and in some cases would cause a sudden stopping of the motor. If, on the other hand, the curve 29 runs approximately parallel to the resistance line 9, the influence of the above mentioned irregularities will be of but little importance, and as a consequence a safe and uniform running of the motor is guaranteed even with very low speed.

The present invention possesses still another advantage over the ordinary generators, namely that it is possible to couple the difierential compound winding with the compounding winding in series. A similar simple coupling is not applicable in ordinary generators; as, with such a coupling, the same effect would simply be attained as if the generator, beside the separated excitation had but one compounding winding with correspondingly fewer number of coils.

l/Vhat is claimed is 1. I11 a separately excited continuous current generator, having separately excited winding a compounding winding and a differential winding for weakening the field: a main magnet-frame carrying said compounding winding and a separate magnetframe carrying said differential winding, the saturation point of said last-named magnet-frame being considerably lower tllil-Ilf. that of the first-named one.

2. In a separately excited continuous current generator, having separately excited winding a compounding winding and a differential winding connected in series therewith for weakening the field; a main magnet-frame carrying said compounding winding and a separate magnetframe carrying said difierential winding, the saturation point of said last-named magnet-frame being considerably lower than that of the firstnamed one.

3. In a separately excited continuous current generator, having separately excited winding a compounding winding and a differential winding for weakening the field, a main magnet-frame carrying said compounding winding and a separate magnetframe carrying said differential winding, point than the corresponding characteristic 10 the saturation point of sald last-named magcurve of the compound windlng. net-frame belng considerably lower than The foregoing specification signed at Barthat of the first-named one and the characmen, Germany, this 2nd day of May, 1911. teristic curve of the differential Winding,

T T representing the functional relation existing KURT GREUL between the electromotive force induced by In presence of said Winding and the armature current CHAS. J. WVRIGHT,

strength, being steeper near the starting ALBERT F. KEEPER.

Copies of thin patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington I). G." 

